A typical type of flared plastic fitting used for fluid flow applications has a flared tube end with a mating nut positioned inboard of the flared end to couple to a corresponding flared fitting. Conventional plastic flared fittings, such as a right angle fitting, are fabricated by molding a straight tube extension as part of the main body of the fitting. The tube extension is heated to a softened state, which can typically take two to three minutes. The tube extension is then inserted through the back side of the mating nut, pushed onto a forming mandrel and allowed to cool. After cooling, which may take on the order of five minutes to as much as ten to twelve minutes for some processes, the mandrel is removed from the now formed flared end.
This technique for forming a flared fitting has several disadvantages. Hot flaring molded fittings is a time consuming and inefficient process, requiring skilled technicians with special tools and equipment. Even so, the process has a typical reject rate on the order of 10% to 30%. Another disadvantage is that hand forming the flare results in lack of precision in the finished part. The trueness of the flared end with respect to the nominal tube fitting axis suffers due to the hand forming. The resulting parts are low tolerance, and this can result in a buildup of tolerances when many fittings are employed in an installation.
The hot flaring technique has also been implemented in semi-automated and automated systems, yet parts fabricated using semi-automated or fully automated systems have been found to have problems of lack of trueness and low tolerances.
It would be advantageous to provide a flare fitting with higher tolerance than afforded by known techniques.
It would also be advantageous to provide a technique for forming flared fittings resulting in higher throughput and which requires less skill than known hand forming techniques.